var RunBackgroundLayer = cc.Layer.extend({
    ctor:function () {
        this._super();
        this.loadBg();
        return true;
    },
    loadBg : function(){
        var run_bg = new cc.Sprite(res_run.run_bg);
        run_bg.setPosition(gg.width * 0.5, gg.height * 0.5);
        this.addChild(run_bg,1);
    }
});